Early onset of kinetic roughening due to finite step width in hematin crystallization

Crystallization is an example of a highly non-equilibrium process, in which the flows of mass and energy are governed by dynamic structures comprising a two-dimensional interface between adjacent three-dimensional semi-spaces. During crystal growth, the structure of its interface with the growth medium dictates the molecular mechanism of solute incorporation, the response of the growth dynamics to temperature and composition gradients, the action of impurities and dopants, and, ultimately, the crystal perfection. Interfaces that are smooth at equilibrium may become rough during growth at elevated supersaturation. We observed a smooth to rough transition during the growth of hematin crystals from a biomimetic mixed organic-aqueous solvent. Hematin crystallization is the main pathway employed by malaria parasites to sequester toxic hematin, released during hemoglobin digestion; its inhibition is considered the most successful target for antimalarial drugs. We show that the transition occurs at a supersaturation significantly lower than that predicted by published criteria.